1. Field of the Invention
The present invention relates to a structural member created by assembling a plurality of wooden members with suitable reinforcing means disposed within recesses within the structural members so as to provide increased load bearing capacity for the structural member. The invention also provides a related method of creating such a structural member.
2. Description of the Prior Art
Engineered wood products, such as glued laminated (glu-lam) beams and columns, structural use panels, such as plywood and oriented strand board (OSB) and the like are in common use today as structural members. The use of composite structural members to increase strength to cost and strength to cross-sectional area ratios is known. Composite structural members are typically stronger and lighter and may be less expensive than similarly sized single material members. The use of wood/wood and wood/non-wood composites enables the use of lower grades of wood in applications where only high grade, high strength woods were utilized previously. As a result, the use of composite structural members encourages more efficient use of natural wood resources.
Prior uses of woven fabrics, such as fiberglass, and thermoplastic composites to reinforce wood members have been less than satisfactory. The difficulty of obtaining a strong adhesive bond between the plastic composite material and the wood has resulted in losing bond integrity under load and over time. The loss of integrity of such bond results in instability of the composite structural member. Another drawback of conventional fiberglass and thermoplastic composites is their susceptibility to fire and the tendency to generate smoke in fire conditions.
It has been known to enhance tensile strength of reinforced fiber composites by pre-stressing the composites with respect to a structural member. It also has been known to provide grooves on all sides of a building member and to mechanically or adhesively secure pre-stressed reinforcing members in such grooves. It has also been known to provide wooden members with grooves which receive adhesively secured, circular, triangular or bull-nosed glass fiber polyester rods for reinforcement. See U.S. Pat. No. 4,615,163.
U.S. Pat. No. 5,026,593 discloses providing a reinforcing strip across the entire width of a wood beam.
U.S. Pat. No. 4,965,973 discloses bonding pre-stressed reinforcing member to a wood beam in order to increase stiffness and bending strength. It has also been known to pre-stress a structure by applying tension to fibers relating to a wooden structural member prior to or during manufacture as by securing the fiber in tension to the wood by adhesion or by mechanical means.
U.S. Pat. No. 4,430,373 discloses the use of reinforcing threads positioned directly within particle board.
U.S. Pat. No. 4,428,791 discloses the use of threads or wires extending in the direction around bars which are positioned around a rotating drum and are secured to the fibers by a binding agent. Adhesive bonds a pair of strands to each other.
U.S. Pat. No. 5,058,339 discloses the use of flat metal bars as stringers inside a curved stairway.
Co-pending U.S. Ser. No. 08/380,858 entitled "Reinforced Composite Structural Member and Associated Method" owned by the assignee of the present application discloses the use of reinforced composite sheet having randomly oriented fiberglass fibers in a matrix of thermosetting resin.
There remains, therefore, a need for a composite structural member and associated method which employs wood members and associated specifically positioned fiber reinforced resin composite members to provide increased load bearing capacity including high bending strength and the reinforced wood assembly while preserving the dimensions and wooden appearance of the structural member.